Patches for rubber articles



June2,1959 RDBOYCE 2,888,972

PATCHES FOR RUBBER ARTICLES Filed Nov. 17. 1953 F 'G- l bf/ /7/ M7721 13 16W/,U4 /A F IG. 4 1 l@ WW2 REG/NA a Dave ww 5a vce,

PATH-ES FOR RUBBER ARTICLES Reginald Donovan Boyce, Denham, England Application November 17, 1953, Serial No. 392,703

2 Claims. (Cl. 152-367) This invention relates to repair patches for rubber or rubberized articles, such as vehicle tire tubes. It is known for a repair patch to comprise a foundation member of cured rubber, shaped with 'a bevelled rim or of bulbous conformation, i.e., the thickest part of the member being in the middle, and the thickness decreasing relatively sharply towards the edges, the foundation member having a protective layer on one side and a layer of adhesive on the other side, and the adhesive layer being protected by a layer of paper, metal foil, or other suitable airtight material. A known modification of this kind of patch has the adhesive layer extending beyond the margin of the foundation member, and protected before use by the protective layer lying against the foundation member. In such a known construction the projecting rim is unprotected during use except for the backing provided by the protective layer, which is usually of paper, and therefore the rim is easily broken up when the patch has been affixed to a tire tube and the tire is undergoing deformation during use. The protective paper cannot be completely removed by hand, but it breaks up into little balls, which cause deterioration or disintegration of the soft rim of adhesive compound. If all the paper could be removed, the unprotected upper surface of the lip would stick to the cover, making tube removal difficult. In addition, poor adhesion occurs between thc edge of the cured foundation member and the soft rim of the adhesive layer. It is an object of the present invention to provide a repair patch overcoming these disadvantages, and a method of manufacture of such a patch.

According to one aspect of the invention, a repair patch for a rubber or rubberized article such as a vehicle tire tube comprises a foundation member of cured rubber having a `layer of adhesive compound on one side thereof, wherein the adhesive side of the patch is convex.

According to a further aspect of the invention, a repair patch for a rubber or `rubberized article, such as a vehicle tire tube, comprises a foundation member of cured rubber having an airtight protective layer on one side thereof and `a layer of uncured adhesive compound on the other side thereof and formed with a rim projecting beyond the margin of the foundation member, and a layer of foil or other airtight material protecting the adhesive layer, wherein the foundation member has a projecting rim of cured rubber co-extensive with the rim of adhesive compound, said projecting rim of cured rubber being of substantially uniform thickness and extremely thin relatively to the foundation member.

Preferably the foundation member comprises a central body of substantial thickness and a layer of cured rubber of extreme thinness extending beyond the margin of the central body and constituting the projecting rim of cured rubber.

The invention also includes a method of making a repair patch, which comprises coating a carrier such as a sheet of paper or linen with a vulcanizable solution or dough; laying said carrier with its coated side against an fqice uncured vulcanizable disc of rubber located on an independently unvulcanizable coating of adhesive which covers a protective layer, to form a stack; pressing said stack with a hot platen into a resilient blanket or the like carried by a cold platen, and thereby uniting the vulcanizing coating, disc, and independently unvulcanizable coating, while simultaneously shaping the disc and partially or completely curing the coatings and disc.

The invention will be described with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic cross-section of a simple form of patch according to the invention,

Figure 2 is a corresponding view showing the patch just before its application to a tyre tube.

Figure 3 is a diagrammatic cross-sectional representation of the layers of another form of patch at an early stage of manufacture,

Figure 4 is a diagrammatic cross-section of this form of patch when finished,

Figure 5 is a fragmentary diagrammatic cross-section, greatly enlarged, of the marginal portion of the patch, and

Figure 6 is a corresponding view, showing the part vulcanization within the patch in diagrammatic form.

Referring first to Figures l and 2 of the drawings, these illustrate one aspect of the invention as applied to the simplest form of patch. All protective llayers are omitted for the sake of clarity. The patch has a body or foundation member 7 formed with a substantially flat surface 7a and a convex surface 7b. A layer 8 of adhesive com-` pound is applied to the convex surface 7b.

Such a patch may have its body 7 formed by moulding, or by the more elaborate technique hereinafter described, but the essential feature is that the adhesive layer 8 is applied to the convex surface 7b. This is in contradistinction to known patches, which have their adhesive surface substantially flat, and not deliberately convex.

Figure 2 illustrates the patch just prior to its application to a vehicle tire 9, shown as having a puncture at 9a. It is not suggested that this attitude of the patch before it is secured to the tire will actually occur in practice. lt will be seen, however, that since the tire has a convex outer surface to be repaired, the patch will eventually be forced into the bowed attitude, and that the convex surface 7b of Figure l `will have been given a reverse curvature. This causes a radial inward compression of the adhesive layer 8, shown in Figure 2 as having a wavy surface to indicate graphically the concertina effect to which its free surface is subjected. I believe that it is due to the inward compression of the adhesive surface, or concertina effect, that such a patch exhibits markedly superior properties of adhesion to the tube, as compared with generally similar known patches having flat adhesive surfaces.

Referring now to Figures 3 to 6 of the drawings, a sheet of aluminum base foil 10 is first coated with a layer 11 of Ian adhesive compound of a thickness of approximately ten thousandths of an inch. This thickness, and indeed all the dimensions specified herein, is purely exemplary, and may be modified in a manner that will be well known to those skilled in the art in accordance with the size and characteristics of repair patch required. The aluminum base foil has a thickness of two thousandths of an inch and is inert or neutral in that it has no effect on the adhesive compound chemically, but forms a physical protection without inducing any chemical changes during the storage life of the article. The foil is preferably one with a veryhigh degree of surface polish or gloss. This is achieved by heat rolling the foil as a nal step in the rolling process by which it is produced, and in addition produces a quasi case-hardening effect on it. it is to be understood that such foil is pref- Patented .lune 2, 1959 3 erable but is not essential to the invention, and other protective layers may be employed. The adhesive is conveniently rolled on to a foil by a calendering process, and in large scale production the adhesive may be laid continuously on a web of foil.

A suitable mix for the adhesive layer may contain the following ingredients:

Brown crepe thin `M-R-X (mineral rubber) Z-O-X (zinc oxide) Asbestine Carbon black Stearic acid The proportions may be selected according to requirements, as will be clear to those skilled in the art.

The coated web is cut into sheet form, the size of sheet being governed by the capacity of the plant available for making the patches. The larger the sheet, the greater the number of patches that can be simultaneously manufactured.

The cut sheet is then laid on a supporting surface, foil side downwards, and an aluminium template (not shown) is laid on top of it. This template consists of a sheet of aluminium having a thickness sufficient to enable it to be handled conveniently and formed with apertures located in rows at spaced intervals, the spacing depending on the size of patch to be manufactured. For reasons of economy the spacing is as close as possible. ln each aperture of the template there is placed a disc of rubber indicated at 12 in Figure 3, ultimately to constitute the main body of the patch. For a circular patch, the rubber disc 12 is circular and of substantial thickness, ie., considerably thicker than the ultimate maximum thickness required of the main body. The rubber is in a partially cured, or preferably uncured, state.

A suitable mix for the rubber for the main body may contain the following ingredients:

Pale crepe Asbestine Best Whitings Z-O-X (zinc oxide) Sulphur Stearic acid Agerite powder Turkey Red D.P.G. (di-phenyl-guanidine) As before, the precise proportions of the mix may be selected according to requirements.

Simultaneously with the above operations a web of paper ultimately to form the protecting layer 13, and preferably of Velltun-type tracing paper, is coated with a curable uncured rubber solution or dough indicated in Figure 3 at 14, the coating being of the order of two thousandths of an inch in thickness. The layer of solutio 14, after application to the pape 13, is allowed to dry and is then dusted with a powder such as french chalk.

The rnix for the solution may be the same as that for the main body, but broken down in a suitable solvent.

After the aluminium template has been removed from the adhesive coated sheet of foil 1u, 11, with the main bodies 12 located thereon, the paper 13 is laid over the sheet, with the solution-coated side downwards. The elements of the patch so far described are thus located in the relative positions illustrated diagrammatically in Figure 3. The stack so constituted is placed with the foil sidefdownwards on a blanket or an air or water bag 17 located on a cold platen 16. This platen 16 is itself located under a hot platen and the cold platen 16 is raised-against the hot platen 1.5 and pressure of the order of 200 lbs. per sq. inch is supplied for several minutes (say three or more) at a temperature of the hot platen 4 15 of the order of 300 F. lt will be appreciated that these pressures and temperatures are by way of example only and may be varied within limits well understood by those skilled in the art.

An increase of pressure is then applied for a further period of several minutes, say two to seven minutes. As is well known, the curing time of a compound may be Varied according to the ingredients in the The platens 15, 16 are then separated, the stack is removed and allowed to cool, and is then punched so as to form separate patches. Reference must now be made to Figure 4. Dun'ng the application of pressure, the main body 12 has considerably decreased in thickness, with a corresponding increase in area, and the upper surface of the stack is subjected to pressure against the rigid hot platen 15, while the lower surface of the stack is shielded from the rigid surface of the lower cold platen 16 by the resilient blanket or bag 17'. While this produces a squashing of the main body 12, it results in ultimate rounding of the lower surface of the main body 12, thc upper surface ultimately adopting a flat conformation.

The lower surface is not of uniform curvature, since the convexity is more pronounced in the middle, the edges, lbeing thinner and more llexible, adopting a slightly flatter curve. The punching out of the patches from the stack is effected in the usual manner, but is arranged so that a lip of appreciable dimensions is left all around the main body, as indicated at 18, outside the broken lines. In other words, the diameter of the finished patch after punching is arranged to be substantially greater than the final diameter of the main body 12.

If it is desired to print any legends on the finished patch, these may be conveniently printed in reverse and in correct register on the under surface of the protective paper layer 13 before the coating of the solution or dough le is applied thereto. Such a course can, it is to be yunderstood, only be adopted when the transparency of the layer 13 is such as to enable the legend to be read. If an opaque material is chosen for the layer 13, then the printing must be done at some other stage of manufacture, but the method described enables the legend itself to be protected against subsequent handling since it is beneath the surface of the protective paper layer 13.

Alternatively, the printing may be carried out in reverse on the protective layer 13, whether opaque or not, using a printing ink that will transfer itself to the patch. This enables a permanent legend to be applied to the actual surface of the patch.

Figures 5 and 6 show the finished patch in greater detail. In Figure 5, it will be seen that the layer of foil 1() is curved while the paper layer 13 and solution layer 14 have conformed with the first shape assumed by the top surface of the main body 12. The layer of adhesive 11 has, however, crept between the margin of the main body 12 and the solution layer 14. The exact behaviour of the adhesive is not understood, but it appears to assume the form of a wave which moves radially inwardly, relatively to the main Ibody, and to have a breaking crest which laps around the margin of the main body.

The effect of this is extremely important, and contributes largely to the efficiency of the patch, particularly in association with the stages of vulcanization which the particles of rubber achieve at various strata within the thickness of the patch. A11 attempt is made in Figure 6 to depict such stages of vulcanization. The various rubber layers 11, 12, and 14 are shown as one area (the main body 12 being demarcated by broken lines) variously shaded to indicate vulcanization. The lighter areas are more completely vulcanized than the darker areas, and, while complete vulcanzation has taken place in the layer 14, and in almost all the main body 12, and the vulcanizing effect can be seen to have crept downwards (i.e., from the hot platen 15), the layer of adhesive 11V is virtually completely unvulcanized at its lower surface. This lunvulcanized area extends only to a small degree into the wave of adhesive that laps around the margin of the main body 12, and the wave tends to bond the main body 12 and the lip 18 together to effect greater strength.

The upper surface of the adhesive is vulcanized to a small and graduated extent by permeation of the vulcan izing effect of the vulcaniaable main body, ensuring a permanent bond between the main body and adhesive layer.

Not only are the drawings purely diagrammatic, as regards the relative dimensions of the various layers, but the degree of vulcanization in the various strata is dependent on the rubber mixes employed, and the heat and pressure imparted by the platens. Such factors will be Well understood by those skilled in the art, and will be chosen according to the dimensions and characteristics required in the finished patch.

A patch made in this way has a cured main body 12 and which is formed with a projecting rim (indicated at 14a in Figure 3) of extreme thinness and lying co-extensive with the projecting rim 11a of adhesive compound. It is to be noted that this extreme thinness, obtained by the use of the initially coated sheets 13, 14, is much less than could be obtained by ordinary moulding of the cured foundation member, although that is not to say that moulding could not be employed to produce a comparable component. The method described is, however, preferable when a rimmed patch is required.

ln use the patch is applied in the ordinary way, that is to say, the protective foil is stripped away and the adhesive layer 11 applied to the article to be repaired. It will be seen that the projecting rim 11a of the adhesive layer 11 is backed by an extremely thin layer 14a of cured rubber, in turn covered (before use) by its own protective layer 13 of paper or linen, and this backing of the adhesive layer 11 with a thin layer 14 of cured rubber around the projecting rim effectively overcomes the deterioration of the adhesive layer hitherto encountered. Ihe protective layer 13 of paper or linen can be removed from the patched tube before it is inserted in the cover, and the rubbing effect of the tire cover is thereby resisted, thus rendering impossible the Abreak-'up of the protective layer into little balls as has been mentioned above. During the running of the tire and due to the heat generated, the thin skin 14a of cured rubber lying over the adhesive rim 11a, combined with the pressure of the inflated tube, will eventually partially or entirely cure the 'uncured rim 11a, so effecting a completely permanent repair.

A patch according to the invention can be applied and vulcanized in a vulcanizing press if desired in two minutes, thus resulting in a great saving of time over known patches. Due to the presence of the cured rim, the margin of the patch can be pressed out to effect a superior union with the tube. The fact also that the exposed surface of the patch is cured protects the repair against the effect of oxidation and provides a good ageing life for the patch. The cured rim is not resilient, since it is faced by the adhesive layer. Thus, if the cured rim is deformed, it is held in its deformed position by the adhesive layer. This results in the cured rim accommodating itself to movements of the main body of the patch, or of the article to be repaired, in a non-resilient, passive, manner, and prevents any initial deterioration of the union between the cured rim and the article to be repaired.

Moreover, porosity and air pockets in the various layers is obviated during manufacture, and the use of glossy foil as a protective layer for the adhesive surface imparts maximum sensitivity to the adhesive surface when the foil is removed to enable the patch to be applied, and prevents the trapping of air between the adhesive surface and the article to be repaired.

I claim:

1. A rubber patch for repair of a rent in the innertube of a tire comprising, a body of partially cured rubber having a substantially flat upper surface and a convex opposite surface meeting in a perimetric tapered edge, a layer of uncured adhesive aflixed over said convex surface and protruding beyond said edge on all sides thereof, an extremely thin layer of cured rubber affixed over said upper surface and protruding beyond said edge on all sides thereof so that said layers present facing surfaces equal in area one to the other surrounding said body, a flexible, peelable protective sheet entirely overlying said cured rubber layer on the opposite surface thereof, a flexible, peelable protective sheet overlying the adhesive layer on its opposite surface, said facing surfaces being adhered together to form an extremely thin, outwardly projecting lip surrounding the body, said lip being of substantially uniform thickness and sandwiched between said protective sheets.

2. A patch as described in claim 1 in which said adhesive layer has a portion thereof adhered between said edge and the cured layer continuously around. said body.

References Cited in the file of this patent UNITED STATES PATENTS 941,047 Shelton Nov. 23, 1909 -1,111,803 Moomy Sept. 29, 1914 1,426,672 Radford Aug. 22, 1922 1,480,976 Wight Ian. 15, 1924 1,690,514 Walter et al Nov. 6, 1928 1,996,285 Eckhart Apr. 2, 1935 2,126,771 Hanson Aug. 16, 1938 2,130,658 Watson Sept. 20, 1938 2,140,692 Daly Dec. 20, 1938 2,238,216 Eger Apr. 15, 1941 2,339,559 Charnes Ian. 18, 1944 2,486,669 Nassimbene Nov. 1, 1949 2,638,955 Gruber May 19, 1953 

